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Articles by Venu Madhavi
22 articles
What MySQL returns if I insert invalid value into ENUM?
If strict SQL mode is disabled and we insert an invalid value (which is not in the list of permitted enumeration values) into ENUM, MySQL will insert an empty string instead of throwing an error. If strict SQL mode is enabled, MySQL throws an error when inserting invalid value. Invalid values without strict SQL mode Strict SQL mode is disabled by default. When it is disabled, if we enter an invalid value that is not in the ENUM list, it returns an empty string. Let us understand this by using the example below. Example In the below example we have ...
Read MoreUse a trigger to stop an insert or update in MySQL?
The MySQL trigger can be used to automatically terminate an INSERT or UPDATE operation if specific conditions are not met. This is achieved by adding logic to the trigger to detect incorrect data or violations of a rule. If the condition is satisfied, the SIGNAL statement is used to show a customized error message and terminate the procedure. Thus, it ensures that the database has valid, clean, and consistent data. For instance, if a value is being updated or inserted in the column beyond the allowed range, the trigger can stop the action and give a customized error message. ...
Read MoreWhat does DELIMITER // do in a Trigger in MySQL?
DELIMITER in MySQL Triggers In MySQL, a DELIMITER command changes the delimiter from its default value of semicolon (;) to another string like //. This is really useful when creating stored procedures or triggers that contain multiple SQL statements, which may also include semicolons. Why do we Change the Delimiter in MySQL When you declare a trigger, you have to write a few SQL statements that may also involve control flow statements like IF conditions, which include semicolons. Unless you change the delimiter, MySQL will consider the first semicolon to be the end of the declaration of the ...
Read MoreWhy should we not store a number into a MySQL ENUM column?
MySQL stores ENUM values internally as integer keys (index numbers) to reference ENUM members. The main reason for not storing the integer values in the ENUM column is that it is very obvious that MySQL ends up referencing the index instead of the value and vice-versa. These indexes begin at 1, not 0, and map to the order of the values defined during table creation. If a number is inserted directly into an ENUM column, MySQL interprets it as the corresponding index, leading to unexpected behavior. Example Let us create a table named Enmtest ...
Read MoreSelect records with ACTIVE status in MySQL set with ENUM
MySQL's ENUM data type is used to define a specific set of values in a column making it easier to manage and maintain data consistency. GROUP BY and WHERE() function In MySQL WHERE clause is used to filter the rows based on a condition before grouping them. The GROUP BY clause groups rows with identical values in specified columns, and can be used with functions like SUM, COUNT, and AVG. Together they enable focused data analysis by filtering and grouping efficiently. Syntax Following is the syntax to filter the data on certain conditions and to eliminate duplicate records. SELECT column1, ...
Read MoreMySQL query to select ENUM(\\\'M\\\', \\\'F\\\') as \\\'Male\\\' or \\\'Female\\\'?
In MySQL, the ENUM data type is used to limit column values to a specified set of options which is useful for categories like colors, status, and gender. Sometimes, it is helpful to display these ENUM values as more descriptive like converting 'P' to "pass" and 'F' to "Fail". The IF() function in MySQL makes this easy by allowing conditional logic within SQL queries. The example below will demonstrate how to use the IF() function to convert ENUM values into user-friendly. Example To understand first let us create a table, DemoTable, which contains an ENUM column UserGender to store ...
Read MoreIn which order MySQL will invoke the triggers if we created multiple triggers of same event and action time?
In MySQL, triggers allow automatic execution of specified actions in response to INSERT, UPDATE or DELETE events on a table. Often, multiple triggers may be created for the same event and action time (e.g.; multiple BEFORE INSERT triggers on the same table). By default, MySQL invokes these triggers in the order they have created. However, the FOLLOWS and PRECEDES option allows control over the sequence of execution which can be critical in complex data handling. In this article, we will explore how to set the order of multiple triggers for the same event and action ...
Read MoreHow to show that each MySQL enumeration has an index value?
In MySQL, the ENUM data type enables you to define a column using only a collection of predetermined values. Each value in the ENUM list is assigned a position number known as an index (which begins with 1). These index numbers represent the positions of the values in the list, not the actual data. For example, if the ENUM list is ('Male', 'Female', 'Other'), Male has an index of 1 while Female has an index of 2 and Other will have an index of 3. This further enables MySQL to store and compare the values more effectively, though actual ...
Read MoreHow MySQL handles the empty and null values for enumerations?
In MySQL, the ENUM data type allows you to create a column with specified values like 'A', 'B', 'C', and 'D'. This feature is useful for maintaining data consistency, as it restricts entry to a specific set of values. However, the behavior of ENUM columns can vary depending on whether the NOT NULL constraints are applied and also depends on SQL modes. How to handle ENUM values with SQL modes MySQL accepts empty values for enumeration only if SQL mode is not set as TRADITIONAL, STRICT_TRANS_TABLES, or, STRICT_ALL_TABLES. Otherwise, MySQL would not accept empty values and throw an error. ...
Read MoreHow is it possible for a MySQL trigger to execute multiple statements?
In MySQL, triggers are a mechanism that allow for specific actions to be executed automatically when specific events like Insert, Update, or Delete occur in a table. They are useful as they automate processes and maintain data integrity. Using BEGIN...END in trigger In a trigger, if we want to perform more than one action we write it within the BEGIN…END block. This block simplifies the way we can manage a larger number of actions for a more complicated task. Let us see how the BEGIN...END construct allows multiple statements to be executed within a trigger. We can group ...
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